I continue to struggle, both with BTL advocacy, and with application of the term, "CO2-neutral", to catalytic coal methanation.
Hank Green the Ecogeek informs us that the NRDC has created a great (and frighteningly accurate) animation to spread the word, while the UoCS has released a report on the dangers of CTL (Coal-To-Liquid fuel) technology.
Again I refer to Jim Fraser1 for a better understanding of the process occurring in the fuidized bed, methanation reactor.
Steam is added to "fluidize" the mixture and ensure constant contact between the catalyst and the carbon particles, generating a gas of predominately methane and CO2. The water gas shift occurs within the methanation reactor eliminating the need for a separate reactor. The catalyst allows the reaction to take place at a lower temperature than typical gasification processes, lowering the cost of materials of construction, lowers the maintenance costs and eliminates high temperature cooling. The use of steam eliminates a costly air separation plant that typically runs at 20% of the total capital costs. The process has an overall efficiency of about 65%.
After methanation the gas is sent to a gas cleaning system where CO2 and other contaminants are removed. In addition, the catalyst is recovered from the bottom of the gasifier and recycled back into the methanation reactor. The byproducts (such as sulfur, nitrogen and CO2) are captured and sold to the chemicals and petroleum industries, resulting in near zero hazardous air or water pollution.
Half of the carbon, in the form of CO2, can be captured and sequestered in local oil wells or coal bed methane mines. In addition, the other harmful contaminants contained in coal are removed including sulfur, nitrogen, arsenic, mercury, and particulates. Once captured, most of these materials are sold to the chemicals industry and the remainder is disposed of in a safe non-leachable manner.
And, the way, Jim, that we know that this process will yield near zero hazardous air or water pollution is that we will have the assurance of the Business Protection Agency (formerly known as the EPA).
According to the EPA (a division of FutureGen the Department of Energy), fossil fuel combustion creates 82 percent of total US carbon dioxide emissions, with coal accounting for about 40 percent of that amount.
Now those of you who don't know me all that well might point out that the above describes coal to methane whereas the BTL advocacy from the AG readership is about Biomass. Well, yes, but with all of the green washing it could be easier to overlook that BTL is a source of GHG.
Still some research does show that getting energy while converting waste biomass into char that is then buried is a good way to avoid releasing greenhouse gases into the atmosphere although such advocates tend to make comparisons to processes that produce more GHG.
Tyler Hamilton opines:
As concentrations of greenhouse gases in the atmosphere reach critical levels, we'll need to start talking more seriously about extracting CO2 from the air rather than simply adding less or none. This means considering technologies that are carbon-negative, and this is where gasification and pyrolysis of biomass becomes interesting.
Using biomass as fuel is itself carbon-neutral, but if we could capture and sequester the CO2 through a gasification process or in the form of a solid char or "biochar" through pyrolysis, then there's opportunity to generate electricity and heat and remove CO2 from the atmosphere.
It's not going to solve all our problems, but certainly 2008 is a year where we see growing interest in biomass gasification and biochar production, even if only on a small, distributed scale.
Char is very much similar to coal, and most everything that I have seen strongly objects to CTL (or, for that matter CBTL). Yet, if you choose this very polluting approach, might as well toss in some coal for good measure, eh?
The ever helpful US Department of Energy’s National Energy Technology Laboratory (DOE / NETL) has released a feasibility study that outlines how to produce 7,500 barrels per day or more of jet fuel or diesel by means of a slurry of coal with a small amount of biomass added. The CBTL (Coal / Biomass To Liquid fuel) proposal is another example of integrated production since “the plant would also produce more than 3,500 barrels per day of liquid naphtha products that can be shipped to a refinery for further upgrading to commercial-grade products or sold as chemical feedstock.” It also improves EROEI by HRSG (Heat Recovery Steam Generator).
So, what are the alternatives. Well, in relaying information from a Science article, “Carbon Mitigation by Biofuels or by Saving and Restoring Forests?”, Joseph Romm2 advises, if our primary goal is mitigation of carbon dioxide-driven global warming, then those implementing biofuel policy in the short term (30 years or so) should focus upon:
The third measure, "conversion of large areas of land back to secondary forest," notes Joe, "provides other ecological benefits", e.g.:
Conversely, when large areas of land are converted to the cultivation of biofuel crops, warns Romm, then additional strain upon the environment may take place.
"For the longer term," advises Romm, "carbon-free transport fuel technologies are needed to replace fossil hydrocarbons."
Joseph Romm3 respectfully disagrees with who he recognizes as "the nation’s top climate scientist": NASA’s James Hansen. According to an op-ed by that "great environmental writer Bill McKibben, the safe upper limit for atmospheric CO2 Hansen believes should be no more than 350 ppm.
Romm writes, "I have spent two decades managing, analyzing, researching, and writing about climate solutions and can state with some confidence that:"
Climate Progress commentator John Mashey observes:
Rather than just quoting a number: we know this depends on trajectory, not just a peak number, i.e., it doesn’t do us much good if we stop at 450 and stay there, as teh climate system will be in disequilibrium for a long time.
It might be prefect plausible to think that there’s no likely way we can keep (a) much below 450, but maybe Hansen is saying that we’d better have a plan to get it back down to 350 (b).
http://climateprogress.org/2007/10/21/another-study-dissing-biofuels/tra... http://climateprogress.org/2007/12/29/bill-mckibben-james-hansen-350-ppm... http://www.typepad.com/t/trackback/316957/4752572 http://www.typepad.com/t/trackback/7710980
Similar Posts: Integrated Biofuel Production - Part 1 Romm-induced Cartoon Head Shakes Green Light to Clean Coal Clean Coal Technology Coal to DME
1GreatPoint Energy Catalytic Coal Methanation 2Another study dissing biofuels 3Parting company with McKibben and, maybe, Hansen
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